Brad Neuberg wrote an intresting post in his blog about using Google Gears on a Weblog This post contains a lot of examples an link to the similar article with useful information on this topic.

Source: Coding in paradise.

Google Gears is an open source browser extension that lets developers create web applications that can run offline.

With help of JavaScript API and 700K size plugin for IE 6.0+ and Firefox 1.5+ you can enable your applications to be offline.

Google Reader is first Google application which demonstrate offline functionality.

Check API on the Google Gears web page